1. Field of the Invention
The present invention relates to an orthopaedic instrumentation assembly, and, more particularly, to an orthopaedic instrumentation assembly used to prepare a proximal femur for a calcar replacement stem.
2. Description of the Related Art
In orthopaedic hip surgery, the femoral head and neck bone is removed and a femoral stem implant is inserted into the proximal femur. In the process of removing the proximal bone, an osteotomy guide is typically used to mark the location for making the bone cuts. U.S. Pat. No. 4,959,066 teaches such an osteotomy guide. A cylindrical reamer is used to ream along the intramedullary canal of the femur and establish an axial reference. The osteotomy guide is attached to the reamer such that the guide lies along the outside of the femur. Indicia on the osteotomy guide are used to locate the guide relative to landmarks on the femur such as the femoral head center, greater trochanter and lesser trochanter. A slot in the guide is then used to mark the location of the bone cut corresponding to a desired implant position. The guide is removed and the femoral bone is cut and removed. Once the head and neck bone are removed, the intramedullary canal is rasped to seat the implant at the desired position. A calcar planer is often attached to the final rasp and rotated back and forth to precisely trim the bone cut made during the osteotomy step.
During an orthopaedic revision surgery, a primary orthopaedic implant which was placed within the bone during a previous primary surgery is removed and a revision orthopaedic implant is implanted within the bone. In the case of a revision surgery on a proximal femur, a femoral orthopaedic implant is removed from the bone and a revision femoral implant is placed within the proximal femur. When the primary femoral implant is removed, the proximal femur is prepared to receive the revision implant. It is often times desirable or necessary to remove a portion of the bone which was lying immediately adjacent to the primary implant. Additionally, it is usually necessary to further prepare and shape the intramedullary canal in which the implant is disposed. Depending upon the condition of the bone, more or less bone may be removed to receive the revision implant. It is desirable to leave as much bone as possible, while still ensuring that the revision implant seats against good bone with properly shaped complimentary mating surfaces.
If an appreciable amount of calcar bone must be removed from the proximal end of the femur during a revision surgery, it is known to use a calcar replacement stem which is specially configured to occupy the removed portion of the calcar such that the calcar replacement stem and proximal femur properly conform to and mate with each other. More particularly, a calcar replacement stem includes a block with a distal ledge extending generally transverse to the anatomical axis of the intramedullary canal in which the calcar replacement stem is disposed. Depending upon the amount of calcar bone removed, the surgeon may select a calcar replacement stem with a distal ledge which is disposed at a corresponding axial distance from the proximal end of the femur (i.e., at a selected location along the anatomical axis of the proximal femur).
To prepare a proximal femur for a calcar replacement stem as described above, a surgeon typically approximates the amount of bone to be cut or measures the bone with calipers. This process may be relatively time consuming and may require that the proximal femur be re-cut to properly mate with the calcar replacement stem. A typical prior art surgical technique for a calcar stem is shown in the Echelon Revision System brochure, published by Smith+Nephew. In this technique an osteotomy guide, similar to those used in primary surgeries, is held adjacent the femur and indicia are used to position it relative to the greater trochanter. Horizontal slots in the guide correspond to the calcar stems and the slots are used to mark the bone for cutting. After the bone is cut to the desired level, a cylindrical reamer is used to ream the intramedullary canal. A mark on the reamer is aligned with the bone cut to establish the reaming depth. After reaming, a series of broaches are impacted into the canal to broach the canal to the shape of the implant. A line on the broach is aligned with the bone cut to establish the broaching depth relative to the bone cut.
One shortcoming of the prior techniques is the reliance on landmarks which in a revision case may be significantly deteriorated or missing entirely. Another shortcoming is that the bone resection level is first determined and then the rasps, and ultimately the implant, are referenced to this predetermined level. In a revision case, the bone is deficient and implant stability may not be obtainable at a predetermined resection level.
What is needed in the art is an orthopaedic instrumentation assembly and method of using the same which provides fast and accurate locating, measuring and cutting of a proximal femur for receiving a calcar replacement stem. Further, what is needed is instrumentation and a technique that ensures both that the implant is stable and that the calcar stem seats on the bone.